Why can't preset-env automatically polyfill the latest features

[myNameIsDu]

input:

const a = 1;
const b = 2;
a ||= b;
const str = 'hello';
str.matchAll(/1/)

config:

{
    "presets": [
        [
            "@babel/preset-env",
            {
                "targets": {
                    "chrome": "50"
                },
                "bugfixes":true,
                "useBuiltIns": "usage",
                "corejs":3
            }
        ]
    ]
}

output:

"use strict";

const a = 1;
const b = 2;
a || (a = b);
const str = 'hello';
str.matchAll(/1/);

can be seen the proposal-logical-assignment syntax has been converted, but String.prototype.matchAll has not been polyfill

If I add the proposals configuration of corejs

{
    "presets": [
        [
            "@babel/preset-env",
            {
                "targets": {
                    "chrome": "50"
                },
                "bugfixes":true,
                "useBuiltIns": "usage",
                "corejs":{
                    "version":3,
                    "proposals":true
                }
            }
        ]
    ]
}

output:

"use strict";

require("core-js/modules/esnext.string.match-all.js");

const a = 1;
const b = 2;
a || (a = b);
const str = 'hello';
str.matchAll(/1/);

So I am curious why the latest features cannot be automatically converted

[nicolo-ribaudo]

What is the difference between the two configs?

[myNameIsDu]

My mistake, I copied another configuration I am editing, I have corrected it, I’m very sorry

[nicolo-ribaudo]

Babel uses this list to determine which polyfills are supported by your core-js version. es.* packages are stable, esnext.* are proposal.

As you can see, the stable polyfill for matchAll (es.string.match-all) has been introduced in core-js 3.1.

Your configure specifies corejs: 3 which means "Babel should generate code compatible with any core-js version": it cannot inject the es.string.match-all polyfill because it would throw with core-js 3.0.
You can specify something like corejs: "3.8" instead, which tells Babel "I'm using at least version 3.8": Babel can them safely inject by default the polyfills introduced after version 3.0.0 of core-js.

[myNameIsDu]

Thank you very much for your guidance. I am trying to explore the principle of babel transformation. I am very lucky to get your help.